I. Field
The following description relates generally to wireless communications, and more particularly to signaling Physical HARQ Indicator Channel (PHICH) resource assignments in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT, NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
In wireless communication environments, a downlink control channel such as, for instance, the Physical Downlink Control Channel (PDCCH), can be transmitted by a base station to an access terminal. The access terminal can decode the downlink control channel to identify resources assigned thereto. The access terminal can further employ the identified resources to decode a downlink packet data channel (e.g., Downlink Shared Channel (DL-SCH), . . . ) transmitted by the base station.
To decode the downlink control channel (e.g., PDCCH, . . . ), the access terminal typically leverages knowledge of a number of symbols used for the downlink control channel. The number of symbols employed for the downlink control channel can be a function of resource elements used for a Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (PHICH). However, conventional techniques (e.g., for time division duplex (TDD) systems, . . . ) oftentimes fail to provide information related to a PHICH resource assignment to the access terminal, which can cause the access terminal to attempt to blindly decode the downlink control channel (e.g., PDCCH, . . . ) by assuming substantially all possible PHICH resource assignments. Moreover, other common approaches (e.g., for frequency division duplex (FDD) systems, . . . ) can leverage signaling a PHICH resource assignment from the base station to the access terminal; yet, typical signaling approaches oftentimes fail to adequately address a scenario where the PHICH resource assignment changes between differing Transmission Time Intervals (TTIs). Due to the foregoing, the access terminal can be subject to increased system acquisition time, elevated complexity of decoding, raised amount of time before successful decoding, and so forth.